Long Dan, Zhu Junda, Mao Xuan, Qin Guo-Qing, Wang Min, Li Gui-Qin, Bo Fang, Long Gui-Lu
Opt Lett. 2025 Feb 1;50(3):852-855. doi: 10.1364/OL.546732.
Exceptional points (EPs) in non-Hermitian systems, where eigenvalues and eigenvectors coalesce, offer unique advantages in state transitions, non-reciprocal devices, and sensing, owing to their distinctive and extraordinary properties. Most prior studies for sensing at EPs focused on mode splitting, with limited focus on leveraging the linewidth broadening mechanism. In this study, we construct an EP by embedding two nanoholes within a microdisk cavity. With nanoparticle adsorption at the edge of the microcavity at the EP, the linewidth of two split modes exceeds the frequency splitting, enabling the use of the linewidth broadening mechanism for nanoparticle detection. By calculating the linewidth of the transmission spectra with or without the adsorption of the nanoparticle, an enhanced linewidth broadening based on the EP is achieved compared to that based on the diabolic point (DP). We observe that the linewidth broadening based on the EP varies periodically with the azimuthal position of the nanoparticle along the edge of the cavity. Specifically, the maximum of the linewidth broadening based on the EP is several times larger than that based on the diabolic point. This paper not only deepens our understanding of non-Hermitian physics in microcavities but also lays the groundwork for future research and applications in high-sensitivity sensing.
非厄米系统中的例外点（EPs），即特征值和特征向量合并之处，因其独特而非凡的性质，在状态转换、非互易器件和传感方面具有独特优势。此前大多数关于例外点传感的研究都集中在模式分裂上，而对利用线宽展宽机制的关注有限。在本研究中，我们通过在微盘腔中嵌入两个纳米孔来构建一个例外点。在例外点处微腔边缘吸附纳米颗粒时，两个分裂模式的线宽超过频率分裂，从而能够利用线宽展宽机制进行纳米颗粒检测。通过计算有无纳米颗粒吸附时传输光谱的线宽，与基于二阶奇点（DP）相比，实现了基于例外点的增强线宽展宽。我们观察到，基于例外点的线宽展宽随纳米颗粒沿腔边缘的方位角位置呈周期性变化。具体而言，基于例外点的线宽展宽最大值比基于二阶奇点的大几倍。本文不仅加深了我们对微腔中非厄米物理的理解，也为未来高灵敏度传感的研究和应用奠定了基础。
